The present invention relates to a method of bypassing a block or an occlusion in an artery. The invention also relates to a catheter system for use in bypassing such a block or occlusion in an artery.
Coronary artery disease is the most common cause of death today. Apart from that, more people suffer from pain and discomfort from the disease than those who die. The cause of these problems is mostly localized blocks, also called stenosis, in the arteries that support the heart muscle with energy and oxygen. Pain or death of muscle tissue occurs when this support ceases or is insufficient.
Today almost all incomplete blocks in these arteries are treated by means of dilating balloons that are placed across the blocks and inflated, whereby the blocked site of the vessel may be widened and the arterial fresh blood may pass again. The irregularities that occur in the vessel wall after such percutaneous transarterial coronary angioplasty (PTCA) are today secured and controlled by means of a so-called stent, e.g. a metal cylinder that also is dilated in the same way when in place over the treated area of the vessel, whereby it is pressed against the vessel wall and will remain there as a support.
The vessel has, however, to be open through the narrow part to enable treatment of the block with a balloon. This is the case for about half the population of the coronary deceased people. The other half will have to undergo coronary artery bypass surgery. During this procedure the block in the vessel is shunted (or bypassed) by means of a conduit usually taken from the person himself, whereby fresh blood is guided from another artery upstream through a new passage past the blocked area into the distal part of such a deceased vessel.
Every year about one million people in the Western World undergo the balloon treatment and another million people have coronary artery bypass surgery. The surgery usually involves the use of extra-corporeal circulation, the heart and lung machine, full anesthesia, open chest and long recovery and rehabilitation periods. After having a PTCA, however, the patient will leave the hospital the next day since no anesthesia was necessary and also no major surgery was done.
According to U.S. Pat. No. 5,830,222 of Joshua Makower, a percutaneous revascularization is obtained by arterializing a distal part of a vein, whereby blood flows from a blocked artery and in a retrograde fashion in this distal part of the vein, or by simply using a portion of the vein as a bypass graft, whereby the part of the vein distal to this portion is cut off. Thus, in both these cases the ordinary function of the distal part of the vein is blocked, which may lead to problems as regards blood drainage from the area of the cut-off distal part of the vein.
A main object of the present invention is to provide a new possibility for many of the patients that undergo surgery today of being treated with a similar method as the PTCA, i.e. awake and with no anesthesia and no major surgery even if the artery in question is totally blocked.
A further object of the invention is to provide such surgery without eliminating the function of parts of veins distal to the block or occlusion in an artery.
This object is attained on the basis of the anatomical peculiarity that most of the arteries in the human body are in very close proximity to a vein draining blood from the same area as the artery supports.
In the case of the heart, the artery and the vein usually are so close to each other that contact is present. Moreover, it is very easy to get access to the venous system of the heart since the coronary sinus, the endpoint of the venous drainage from the heart, is easily accessible in the right atrium, only about 20 cm from the patient""s neck and is connected to the big jugular vein in the neck.
Further, an observation that is of great importance for the present invention is the fact that the veins are usually much greater in diameter than the arteries. According to the invention, a covered stent of smaller diameter than the vein is used to bypass the block in the adjacent artery without blocking the flow in the vein itself. Thus the covered stent is positioned in the vein and its ends are connected to the adjacent artery on either side of the block therein.
In this context, the covered stent is essentially equivalent to a vascular graft or a stented vascular graft. In this application, a covered stent is to be understood as a vessel which is flexible, may be dilated and will maintain its dilated shape.
More precisely, the above objects of the invention are achieved by a method and a catheter system as defined in the independent claims. Preferred embodiments of the invention are defined in the dependent claims.
Thus, a method of bypassing a block in an artery which extends along a vein, comprises the steps of forming a first connection between said artery and said vein proximal to the block in the artery, forming a second connection between said artery and said vein distal to the block in the artery, introducing a covered stent through said artery proximal to the block therein, through said first connection into said vein, via said vein to and through said second connection, and into said artery distal to the block therein, such that a proximal end of the covered stent is positioned in the artery proximal to the block therein and a distal end of the covered stent is positioned in the artery distal to the block therein, and fixing the proximal and distal ends of the covered stent within the artery.
The forming of said first connection preferably comprises introducing a first catheter through the artery, said first catheter having a lateral opening at a distal end thereof, positioning said lateral opening so as to face said vein proximal to said block, introducing a first therapeutic wire through said first catheter, said first therapeutic wire having an active distal end, advancing the distal end of the first therapeutic wire through the lateral opening of said first catheter, out of the artery and into the vein, thereby forming the first connection.
The forming of the second connection preferably comprises introducing a second catheter through the vein, said second catheter having a lateral opening at a distal end thereof, positioning said lateral opening so as to face said artery distal to said block, introducing a second therapeutic wire through said second catheter, said second therapeutic wire having an active distal end, advancing the distal end of the second therapeutic wire through the lateral opening of said second catheter, out of the vein and into the artery distal to said block, thereby forming the second connection.
It is most preferable to include a step of catching the distal end of the first therapeutic wire and retracting it through the vein, the first therapeutic wire then extending through the artery proximal to the block, through the first connection and through the vein proximal to the block. As a result, proximal ends of the first and second therapeutic wires extending through the vein may be joined to each other, preferably outside the body, and the first therapeutic wire may be retracted through the artery, such that the second therapeutic wire extends from the artery distal to the block, through the second connection, via the vein to and through the first connection and into the artery proximal to the block, and finally along the artery proximal of the block.
Concluding, the covered stent could be introduced on the second therapeutic wire for bypassing the block and be fixed by dilation of the stent, preferably by means of a balloon.
It should be noted that the stent should be dilated to a diameter which is smaller than the diameter of the vein enclosing part of the covered stent.
In order to position the lateral opening of said first catheter so as to face said vein proximal to said block, a detector is introduced into the vein for detecting the position of the lateral opening in the first catheter. This detector is used first to detect the positions of the block in the artery and then to detect the position of the lateral opening in the first catheter.
The position detector may be an ultrasonic transducer, which is used to detect the position of an ultra-sound reflecting marking, provided on the first catheter in a predetermined relation to the lateral opening at the distal end thereof.
The positioning of the lateral opening of said second catheter so as to face said artery distal to said block may comprise providing a detector on the second catheter and close to the lateral opening thereof for detecting the position of the artery distal to the block.
Preferably, an ultrasonic transducer is used as position detector on the second catheter.
The ultrasound transducers may have the capacity of viewing in a more limited sector and/or 360xc2x0 around the catheter. Further, the ultrasound transducer should be capable of penetrating and depicting structure outside the vessel of its own location, i.e. beyond the wall of that vessel and into adjacent tissue or vessels.
According to the invention, a method of bypassing a block in an artery which extends along a vein, may alternatively comprise the steps of providing a covered stent having a proximal end and a distal end, positioning the covered stent within said vein having its proximal end introduced into said artery proximal to the block therein and having its distal end introduced into said artery distal to the block therein, connecting the proximal end of the covered stent to the artery proximal to the block, and connecting the distal end of the covered stent to the artery distal to the block.
The covered stent used should preferably have a diameter which is smaller than the diameter of the vein enclosing part of the covered stent.
The catheter system of the invention for use in bypassing a block in an artery and performing the above method preferably comprises four components. These components are an arterial catheter, an intravenous catheter, a guide-wire system, and finally a covered stent used as graft.
According to the invention, the catheter system comprises an arterial catheter for introduction into said artery, a distal end of the arterial catheter having a lateral opening to be positioned proximal to the block in said artery, and a wire having a cutting tip at a distal end thereof, said wire being advanceable through the arterial catheter so as to project the cutting tip out through the lateral opening at the distal end of the arterial catheter and thereby laterally out through a wall of the artery.
The arterial catheter may have a flap connected to a distal edge of the lateral opening, said flap being inclined towards the opposite side of the arterial catheter and having a free end proximal of said distal edge. Preferably, the flap is flexible to a position substantially covering the lateral opening of the arterial catheter.
The catheter system may use ultrasound technique for the determination of position. Then, an ultrasound reflecting material is fixed in a predetermined position relative to the lateral opening of the arterial catheter. Preferably, this ultrasound reflecting material at least partly encircles the lateral opening of the arterial catheter.
The catheter system may further comprise an ultrasound catheter for introduction into a vein extending along said artery, which ultrasound catheter may comprise an ultrasonic transducer for determining the position of the block in the artery and for monitoring a positioning of the lateral opening of the arterial catheter when introduced into said artery so as to face the vein.
Preferably, the ultrasonic transducer is directed laterally substantially in the direction of the laterally directed distal opening and positioned distal to the laterally directed opening.
It should be noted that the invention may be used for any pair of an artery and an adjacent vein in the body and not exclusively for such pairs in the heart.